While the present invention is described with particularity as related to forage boxes, it is understood that the present invention has application in numerous other applications requiring coupling a prime mover to a driven mechanism. There are many such applications, particularly in the field of agricultural implements where the prime mover is a tractor driven power takeoff and the driven mechanism is on an implement that is separate from, but powered by the tractor.
Forage boxes are typically towed behind a tractor and are utilized to transport livestock feed from a field where the feed is grown and harvested to a site where the feed is either stored or provided to livestock for consumption.
The forage box typically has a plurality of different mechanisms for unloading the food product that is being transported in the forage box. The first such mechanism is a cross conveyor or auger that operates laterally with respect to the longitudinal axis of the forage box to discharge food product from an opening located in a side of the forage box proximate the front end thereof. Rotating beaters are located generally above the cross conveyor to direct the food product onto the cross conveyor. Additionally, aprons, which are chain-drawn bars that are pulled along the floor of the forage box from the rear to the front of the forage box act to bring the food product forward for interaction with the beaters and cross conveyor. The forage box preferably utilized with the present invention incorporates a separate lever for both engaging the rotatable beaters and for selecting the speed of the aprons.
The unloading mechanisms of the forage box are typically powered by connection to the power take off (PTO) of a farm tractor. The PTO rotates at a selected speed and imparts rotational motion to the unload mechanisms of the forage box through a transmission. A clutch mechanism may be incorporated between the PTO and the transmission of the unload mechanisms in order to provide control of the unload mechanisms from the front of the forage box without recourse to starting and stopping the PTO at the tractor controls.
The clutches utilized on forage boxes and many other implements typically have two sheaves. The driving sheave imparts rotational motion to the driven sheave by means of multiple belts. Clutch engagement and disengagement is controlled by an idler pulley that increases or decreases tension on the plurality of belts as desired. A problem that occurs with current implement clutches is that when the sheaves get rusty during storage or if belt dressing has been used to increase belt traction, the belts do not immediately disengage from the sheaves when the pressure of the idler pulley is removed form the belts. This results in the driven mechanisms, such as the beaters of the forage box, continuing to run on after disengagement has been commanded. The clutch is typically covered by a shield. The shield then has to be removed to free the belts, exposing the operator to the still rotating clutch components. The PTO should also be disengaged before attempting to free the belts. Having to take such actions can be dangerous, time-consuming, and frustrating for the operator.
A related problem is the need for an emergency stop function that will immediately disengage the implement clutch from the PTO and immediately stop the driven mechanisms. The emergency stop function is needed to ensure the safety of operators of the implement. For example, in the event that an operator's clothing or the like becomes caught up in one of the unload mechanisms of a forage box, there is a need to immediately stop the unload mechanisms in order to prevent injury or death to the operator. Accordingly, a clutch that runs on after disengagement of the idler pulley contributes to an emergency situation.
The better forage boxes have provided a mechanism to vary the speed of the aprons so that the speed of delivery of the feed to the auger or blowers that inject the feed into the silo can be changed. Changing the apron speed accommodates the varying rates at which the feed can be conveyed into the silo. The variation in speed is typically achieved through the transmission. Although many types of transmissions can be successfully employed, the transmission usually has a variable speed drive commonly called a variable speed sheave. The sheave system consists of two rotating sheaves spaced apart and connected by an endless rubber belt. Each of the two sheaves has a fixed disc and a movable disc that together form the sheave. The interior face of each disc is angled inward toward the center axial shaft of the sheave. Taken together, the two angled discs form a V-shaped groove with the apex of the V at the center shaft. Varying the spread of the V effectively varies the diameter of the sheave that the belt rides in.
The movable disc is capable of moving laterally with respect to the fixed disc on the common axial shaft such that the movable disc is positionable either very close to the fixed disc or the movable disc can be moved apart from the fixed half. Varying the distance apart of the two discs effectively changes the spread of the V and the resulting diameter of the sheave over which the belt rides. Since the belt is fixed in length, it can be seen that as the movable disc of one of the sheaves moves closer to the fixed disc, the movable disc of the second sheave must move further apart from the fixed portion, thereby decreasing the effective diameter on the second sheave. The two sheaves then function as two gears of variable gear ratio to provide the variable drive speeds for the aprons.
One of the two sheaves, the driven sheave, is driven by the power takeoff (PTO) unit from a tractor through the clutch. When engaged, the clutch supplies power from the PTO to the augers. The driven sheave directly powers the beaters at a constant speed with respect to the speed of the PTO. The second of the two sheaves, the slave sheave, is connected to the aprons in the bed of the forage box. As the two sheave discs of the driven sheave are brought closer together the rotational speed that is imparted to the slave sheave is increased proportionally as a function of the fact that the rotational speed of the driven disc remains constant as determined by the speed of the PTO, while the effective diameter of the driven sheave groove in which the belt rides is increased. This increases the rotational and lineal speeds of the belt. At the same time as the diameter of the driven sheave is increasing, the diameter of the slave sheave is decreasing. The increased speed of the belt and the decreased diameter of the slave sheave results in the slave sheave being driven at a greater rotational speed, in turn resulting in a greater speed being imparted to the aprons.
A shifting mechanism has been provided in the past so that operator of the forage box can engage the feed delivery mechanisms and select the speed of the aprons as desired. These selections were effectively limited only to times when the PTO was engaged. The shift assembly was a bar manually rotated by the operator acting through a lever-like handle affixed to one end of the bar. Through a number of engaging mechanisms, the shift assembly directly controlled the distance of the movable disc of the driven sheave from the fixed disc of the driven sheave and thereby controlled the gear ratio of the variable speed sheave. To achieve a higher speed of the aprons, the shift assembly was rotated to bring the movable disc of the driven sheave closer to the fixed disc of the driven sheave. Conversely, reduced apron speed was achieved by moving the movable disc further from the fixed disc, thereby reducing the effective diameter of the driven sheave.
Removing crops from the field is a time sensitive operation. The window of opportunity for harvesting the crops is frequently determined by nature and is often very time-compressed. Weather conditions will dictate whether the field is accessible to equipment, and will also effect the water content of the crop to be harvested. Once the window of opportunity opens, long hours are required in the field that often extend through the night. A number of forage box loads from the field are required to remove a single day's or night's harvesting efforts. A breakdown of the forage box can have disastrous results, in that the entire harvesting operation may have to be halted while repairs are effected. Such work stoppages can be very costly and exceedingly frustrating for the operator.
The direct connection between the operator's lever and the movable disc of the driven sheave has been a source of breakdowns as indicated above. With the PTO unit from the tractor engaged and with all the feed delivering mechanisms already operating, shifting to a higher or lower apron speed generally presented no problem. This was especially true if the change from one speed to another was done gradually, that is, the rotation of the shift assembly was not abruptly made by the operator. Gradually changing the apron speed gave the driven sheave time to relatively slowly either compress or expand, thereby permitting the belt to ride either further up or down without binding as the belt rotates within the sheave through a number of revolutions.
The most serious problems have occurred in the selection of a higher speed when the PTO unit is disengaged, either by not being powered by the tractor or when the intervening clutch is disengaged and the PTO shaft is rotating. In this condition, the feed delivering mechanisms are not rotating at all. The transmission belt is stationary within the non-rotating sheaves in the position of the speed at which the feed delivery mechanisms were running when the forage box was last powered down.
The operator will tend to exert a great deal of pressure on the lever of the shifting mechanism in order to preselect a higher speed when the PTO is later engaged, resulting in the compression of the belt firmly within the two discs of the driven sheave. When the PTO is then engaged to the transmission, the belt will remain pinched within the driven sheave. The belt accordingly buckles under the driven sheave and effectively tries to wrap itself twice around the driven sheave. The belt will separate because of the tremendous forces exerted by the PTO. Alternatively, the belt may be cut by the supporting flanges beneath the driven sheave as the pinched belt is pulled under the driven sheave. In either case, the belt will be severed and the forage box apron mechanisms will cease to operate. Time-consuming repairs are required to replace severed belts.
Belts can also sever when a high apron speed is rapidly and forcefully selected with the feed mechanisms operating at a low speed. The operator's brusque, forceful rotation of the operator's lever can immediately capture the belt and wrap it beneath the driven sheave, where it is subject to being torn as indicated above.
What is needed is a forage box in which the speed of the aprons can be safely and reliably preselected while the PTO unit is disengaged from the forage box, and that is immune from damage when a higher speed is selected from a lower speed in a brusk manner. A simple and reliable preselection mechanism should be included that can function with the existing drive mechanism for the various feed delivering mechanisms. The preselector should be of the type that is easily understood and actuated by the operator of the forage box. Such a shift mechanism should not include the addition of complex hydraulic or electric actuators that will entail their own maintenance problems. A simple, reliable mechanical device is much preferable.
There is also a need in the industry for a clutch that can be used with a forage box or other implement that stops virtually immediately upon command and for a safety mechanism to provide an emergency stop command to the clutch from a number of positions proximate the implement, but remote from the clutch.